There are always exceptions

Ignore all rules

"If a rule prevents you from improving something, ignore it." (Ignore all rules)

Break them

"By all means break the rules, and break them beautifully, deliberately and well." (The Elements of Typographic Style)

But only if you already know what you are doing

"However, this concept of breaking the rules is only helpful if you already know what you’re doing. (What to consider when considering data vis rules)